This invention relates to a process for producing polyester yarn which is capable of being dyed in yarn or fabric form to a variegated appearance, to systems and apparatus for such treatment, and to the resulting dyed or undyed polyester yarn and fabric made therefrom.
The random dyeing of polyester yarn to obtain a variegated appearance, whether of contrasting tones of a single color or of several colors, is a commercially desirable result since the resulting yarns and fabrics exhibit a pleasing appearance in whatever forms the yarns or fabrics may be used. The variegated effect, however, is difficult to achieve by dyeing techniques alone because polyester yarn is notoriously resistant to dyeing. Furthermore, although dye assistants and dye resists are known, it is difficult to pretreat the yarn before dyeing to obtain truly random coloration.
U.S. Pat. No. 3,155,754 to Adams discloses pretreatment of unoriented polyester yarn with certain semisolvents in order to make the yarn more receptive to dyeing. This patent nevertheless does not teach how the dyeing may be randomized.
U.S. Pat. No. 3,906,757 to Arimoto et al. teaches apparatus for the continuous dyeing of polyester yarn utilizing applicators having bore diameters of 0.25 mm., and intermittent dyeing by dyeing only on discrete sides of the yarn or by interrupting the dye flow.
U.S. Pat. No. 3,724,997 to von der Eltz et al. discloses space-dyeing by injection of dyestuffs into bobbins of yarn positioned on a heated conveyor belt. U.S. Pat. No. 3,153,106 to Schlick teaches variegated dyeing of polyester yarn by heat treating the yarn at spaced intervals prior to dyeing. These techniques are either unduly expensive or do not give good color contrast and variegation.
Other patents which suggest techniques and apparatus for pretreatment of yarn before dyeing, but utilizing complicated procedures and devices, are U.S. Pat. Nos. 2,678,024 to Kresse and 3,589,854 to Cobb et al.
While it is generally known that disperse dye receptivity of a polyester yarn may be increased by treatment with certain polyester solvents, as discussed by Lemons et al. in American Dyestuff Reporter, Jan. 31, 1966, pages 11-17, or of polyester film, as in U.S. Pat. No. 3,446,886 to Karickhoff, such teachings do not suggest how polyester yarn can be rendered capable of being dyed to provide a variegated appearance, whether the dyeing is effected on the yarn itself or on fabrics made from the yarn. The problem is how to treat polyester yarn so that any of the conventional disperse dyeing techniques can thereafter be used to produce a variegated effect, whether on the yarn itself or on fabrics made from the yarn.